The present invention relates generally to components that are used in a vapor deposition chamber, and, more particularly, to shields and retainer rings with features that greatly reduce the amount of contaminants produced by delamination or exfoliation of sputtered material from such shields and retainer rings.
The need to have a clean environment for manufacturing processes in many different industries is well known. The clean environment is especially important when the manufacturing process involves the application of thin film materials, which, in many instances, have thicknesses on the same order as microcontaminants. In these cases, microcontaminants affect the properties of the thin film materials. Therefore, the existence of microcontaminants is a significant problem in these processes.
Vapor deposition systems have a process chamber, in which thin films are deposited. Since thin film deposition is carried out repetitively in the process chamber, a laminated film is likely to be formed on the interior wall of the process chamber. When the total thickness of the laminated film stack deposited on the interior wall exceeds a certain level, it begins to exfoliate. Exfoliation is caused by different thermal expansion coefficients within the film stack and interior wall of the process chamber, or due to membrane stresses within the laminated film itself. Exfoliation generates particles which may be in turn incorporated into thin films deposited on to substrate resulting in defects such as pinholes or contaminants within the film. Therefore, the interior of the process chamber must be cleaned before the thin film exfoliation starts. In a chemical vapor deposition system, a chemical etch is often used between deposition cycles without actually removing the deposition system from operation. However, this etch does not always remove deposited films.
Physical vapor deposition involve depositing thin films on a substrate or wafer in an evacuated chamber. In this process, a target material is bombarded with gaseous ions. The gaseous ions dislodge atoms from the target material. The dislodged material either follows a ballistic trajectory or is focused in the direction of the substrate or wafer to improve the efficiency of the process. The sputtered material adheres to both the substrate and its surroundings. Target materials which are sputtered onto a substrate or wafer, collect also on the process chamber walls. Since most chamber walls are planar and continuous, stresses in the deposited thin films materials builds rapidly across the entire film until the stresses reach a critical point. Stress is then released within the film through buckling or exfoliation from the adhered to surface(s) of the process chamber. This causes small pieces (particulates) of sputtered material to be released into the vapor deposition chamber. These microcontaminants then reach the substrate and can significantly affect the properties of the thin film.
One solution is to facilitate the removal of deposited films which have been sputtered onto chamber walls. This is accomplished with the installation of a removable shadow shielding system. This system does not prevent the materials from being sputtered inside the chamber and does not prevent or reduce the stresses in the thin films deposited across the surface of the shadow shielding system. However, this removable shadow shielding system allows a user to remove the shields and quickly install clean ones. This reduces the overall time that the manufacturing process chamber is removed from operation and production while these films are removed.
The shadow shield is placed around the substrate or wafer in order to reduce the amount of sputtered material from reaching the vapor deposition chamber walls. Furthermore, a retaining ring is sometimes used to hold the wafer in place within the vapor deposition chamber. These components only reduce the microcontamination problem since the sputtered metal collected on the shield or retaining ring will eventually buckle or delaminate, contaminating the chamber and/or the wafer.
Many attempts have been made to create vapor deposition chamber components which reduce or eliminate exfoliation or buckling of deposited thin films. One method of reducing microcontamination is to create a random and micro-rough surface on the vapor deposition component(s). One example of such a component is a sputtering shield that is disclosed in U.S. Pat. No. 5,202,008, by Talieh et al. (xe2x80x9cTaliehxe2x80x9d) wherein the sputtering shield is bead blasted and sputter etched clean to create a micro-rough surface for adhesion of sputtered material. The micro-rough surface may allow an increase in nucleation sites which should minimize the formation of interface voids, thereby reducing the amount of microcontaminants. Another example of a sputtering shield is disclosed in U.S. Pat. No. 5,391,275, by Mintz (xe2x80x9cMintzxe2x80x9d), in which the sputtering shield and clamping ring are bead blasted, ultrasonically cleaned, and, either: 1) sputter etched cleaned, 2) plasma reactively cleaned, or 3) plasma nonreactively cleaned. These processes create the same rough surface as taught in the Talieh patent. It is even known that attaching a layer of microcrystalline alumina (Aluminum Oxide, A1203) on the surface of a sputtering shield helps reduce the microcontaminants. The micro-roughening of the surfaces of these components reduces the amount of microcontamination within a vapor deposition chamber, but there is still a need for further reduction of these microcontamination amounts.
Another method for reducing microcontaminants is to paste or coat the sputtered material onto the surface of the vapor deposition components. An example of such a method is disclosed in U.S. Pat. No. 5,382,339 by Aranovich (xe2x80x9cAranovichxe2x80x9d). Aranovich teaches the pasting of previously deposited material onto the surface by sputtering a material such as aluminum or titanium on top of the previously deposited material. This pasting holds the potential exfoliants to the surface and prevents buckling. However, this pasting, which is equivalent to lacquering, merely adds another layer of material on top of the potential exfoliant which could also buckle as well. Furthermore, this method of pasting or coating increases the complexity of the process, and, while helpful, it is not a final solution to the problem. These methods and devices serve to reduce the problem of stray particulates in the clean environment necessary for thin film deposition, but there remains a further need for vapor deposition chamber components which reduce, or even eliminate, the problem of exfoliation contamination.
Therefore, there is a need for improved vapor deposition chamber components which inhibit or prevent the formation of microcontaminants in a vapor deposition chamber.
A need exists for a method of making a vapor deposition chamber component surfaces which inhibit or prevent the formation of microcontaminants in a vapor deposition chamber that includes the step of selectively etching portions of the surface thereby creating a discontinuous surface to relax stress within deposited thin films.
Moreover, a need exists for a vapor deposition chamber component, such as a shield or retaining ring, that has such a discontinuous surface. The discontinuous surface is defined as a surface with features such as a plurality of projections, cavities, channels or grooves, partitions, or combinations thereof or equivalents.
Yet another need exists for a vapor deposition chamber component with a discontinuous surface that accumulates thin films not deposited on the substrate onto a vapor deposition chamber component surface and secures the thin films to the surface while inhibiting their exfoliation. Therefore reducing the amount of microcontaminants inside the vapor deposition chamber.
Moreover, a need exists for a vapor deposition chamber components which have projections, cavities, channels or grooves, partitions, or combinations thereof or equivalents thereof with a variety of acute angles in order to prevent microcontamination of the clean environment of the vapor deposition chamber.